ISSN: 2574-1241 Volume 5- Issue 4: 2018 DOI: 10.26717/BJSTR.2018.10.001930 Koray Ak. Biomed J Sci & Tech Res

Review Article Open Access

Atrioventricular Canal Defects: Morphologic Features and Surgical Techniques

Koray Ak* Department of Cardiovascular Surgery, Marmara University School of Medicive, Turkey

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*Corresponding: September author: 29, 2018; : October 23, 2018 Koray Ak, Kalp ve Damar Cerrahisi AD, Sağlık Bakanlığı Marmara Universitesi, Pendik Egitim ve Arastirma Hastanesi, 4. Kat, Ustkaynarca Pendik, Istanbul, Turkey

Abbreviations:

International Pediatric And Congenital Cardiac Coding (IPCCC); Atrial Septal Defect (ASD); Cardiopulmonary Bypass (CPB)

Introduction

with partial AV canals. In AV canal defects, aortic valve loses its After the first successful repair of an AV canal defect by C. wedged position between the left and the right AV valves. Walton Lillehei in 1955, there have been tremendous improvements in both surgical techniques and perioperative care of patients. From surgical point of view, one of the most important Nowadays early mortality after surgical repair has dropped to less morphological features of AV canal defects is the location of 3 to 4 % in many parts of the world. On the other hand, in terms the conduction system. Here, atrioventricular node is displaced of complexity, the repair of an AV canal defect could be quite inferiorly and posteriorly toward the coronary sinus due to the challenging for surgeons in some cases. When we look at Aristotle presence of an ostium primum ASD (Figure 1). With this regard, a scoring system which grades congenital cardiac procedures with special attention should be paid during surgical repair in order to regard to their complexity (simple: 1.5 to very complex: 15), prevent the development of complete AV block. surgical repair of an complete AV canal has been still classified as a comlex procedure (Aristotle score 9) [1]. Therefore, in this paper we try to summarize current surgical techniques used for repair of thisSurgical complex Anatomy pathology. and Classification of AV Canal Defects

According to the International Pediatric and Congenital Cardiac Coding (IPCCC) system [2]; AV canal defects have classified into 4 main categories: Figure 1: a) complete, a. Inlet/Outlet ratio in a normal heart is equal to 1, and b) partial, Inlet/Outlet ratio in a heart with AV canal defect is less than 1 c) intermediate/transitional and b. left ventricular outflow tract in a normal heart and hearts with V canal defects. d) AV canal with ventricular imbalance.

Common morphological features of AV canals are described Partial-Type: as deficiency of a portion of the inlet interventricular septum, attachment of a portion of the AV valve to the septum and equal It is a crescent shaped defect of the atrial septum distances of two AV valves to the cardiac apex (Figure 1a). Due and is also named as an ostium primum atrial septal defect (ASD). to the abnormal attachment of the anterior medial leaflet, the Anatomically, bridging leaflets attach to the ventricular septum left ventricular outflow tract seems elongated and sometimes with leaving only an interatrial connection. Despite the presence of obstructed (Figure1b). That might be more prominent in patients a single valve annulus, there are two valvular orifices. In partial AV

Biomedical Journal of Scientific & Technical Research (BJSTR) 7718 Biomedical Journal of Scientific & Technical Research Volume 10- Issue 2: 2018

canal, the AV valve has usually 6 components and the commissure between the left superior and inferior leaflet is called as cleft (Figure 2). Partial AV canals have varying degrees of malformation of the left AV valve, causing varying degrees of valvular regurgitation.

Figure 4: Rastelli classification of complete AV canal defects.

a) Type A:

The superior bridging leaflet has chordal attachments to the septum and normal arrangement of the rightb) ventricularType B: medial papillary muscle.

Figure 2: Partial AV canal defect with a cleft on the left The superior bridging leaflet extends farther atrioventricular valve. into the right ventricle, being attached to an anomalous right ventricular papillary muscle arising from the trabecula Intermediate or Transitional Type: septomarginalis.c) Type C: There is a primum ASD in The free-floating superior bridging leaflet association with a restrictive VSD with this type of the defect. This extends even farther into the right ventricle and is attached to type is distinguished from complete AV canal two separate valvular Surgicalan anterior Techniques papillary muscle. orifices and the presence of a restrictive ventricular defect. Again, there is a single annulus, a common morphologic feature of all types of theAV defects. Canal with Ventricular Imbalance: For surgical repair of all types of AV canal defects, aortic and Due to the presence bicaval cannulation (metal-tipped angled cannulas) is done in a of asymmetrical commitment of the common AV valve to both standard fashion. Surgical repair of AV canal defects are usually done ventricles, one of the ventricles remains hypoplastic (Figure 3). under either normothermic or mild to moderately hypothermic Single ventricle palliation or two ventricle repair could be options cardiopulmonary bypass (CPB) and cold blood cardioplegia in in surgical treatment of these patients. our institution. Repair is standardly perfomed through the right atriotomy.Repair of Partial AV Canal Defects

Repair of partial AV canal defects starts by floating of the valve with injection of saline (or cold cardioplagia solution in some centers). Injection of testing solution should be given to prevent frothing in the left heart chambers. Frothing might cause formation of microbubles within the left heart and, consequently, results in coronary embolisation and ventricular dysfunction during weaning off CPB. During testing of the valve, particular attention should be given to ensure accurate approximation of the cleft. Firstly, we start putting an approximation suture (usually 6 or 7/0 Prolene) from the free edge that is defined by the origin of the cords. Then Figure 3: AV canal defects with ventricular imbalance. multiple simple sutures are employed till the nadir of the cleft. Then, repeat testing of the valve comfirms the competency of the valve. Complete AV Canal: In case with dilated AV annulus, centrally located insufficiency With this type of morphology, there persists after closure of the cleft and it can be treated by placing are a large ostium primum atrial septal defect (ASD) and a commisuroplasty sutures. After repair of cleft, an appropriately large interventricular communication between the crest of the sized patch is sutured to the leaflet tissue between the left and interventricular septum and the inferior aspect of the common right AV valves, that necessitates special attention. Here, suturing valve. The valve might have 5 to 6 leaflets. There are always superior the patch material to the leaflet could cause laceration of the tissue, and inferior bridging leaflets. Based on the degree of bridging and leading to residual leak. The patch material is usually autologous or chordal attachment of the superior bridging leaflet, complete AV bovine pericardium (Figure 5). canal is classified into 3 types by Rastelli in 1966 (Figure 4).

Cite this article: 7719 Koray Ak. Atrioventricular Canal Defects: Morphologic Features and Surgical Techniques. Biomed J Sci&Tech Res 10(2)-2018. BJSTR. MS.ID.001930. DOI: 10.26717/ BJSTR.2018.10.001930. Biomedical Journal of Scientific & Technical Research Volume 10- Issue 2: 2018

for atrial defect autologous or bovine pericardium are used. Some authors do not prefer to divide the superior and inferior bridging leaflets during the repair of the ventricular defect. To improve the exposure, some chord attaching to the leaflet tissue away from the free margins needs to be cut. The rest of the repair is completed standardly (Figure 8).

Figure 5: Closure of cleft and repair of partial AV canal defect.

Repair of Complete AV Canal Defects Figure 7: The AV leaflets are sandwitched between setral crest and the patch in modified technique. Classic Single-Patch:

The classic single-patch technique uses a single pericardial patch to achieve this goal. Fresh or glutaraldehyde- treated autologous pericardium is the choice of patch material with this repair. One of the most critical point of the procedure is the partition of the common valve (superior and inferior bridging leaflets) into two appropriate halves. The common AV valve is cut, and the patch is inserted in such a fashion that the lower portion of the patch closes the ventricular component of the defect, the AV valves are suspended to the patch, and the upper portion of the patch closes the atrial component (Figure 6).

Figure 8: Double patch repair by division of the leaflets.

Conclusion

Partial AV canal defects represents approximately 25% of all AV canal defects. Although these defects show very similar physiology with secundum-type ASDs, there are known to be more complex in terms of morphology. Currently, the perioperative mortality and postoperative complete heart block rates have been reported to be minor after repair of partial AV canal defects. On the other hand, the most common indications for reoperation after surgery remain to be Figure 6: Classic single patch repair. left AV valve dysfunction (almost 10%) and left ventricular outflow tract stenosis (10 to 15 %) in the long term [3]. After repair, in Modified Single-Patch (Australian) Technique: The main addition to the fixation of the valve leaflet to the scooped-out septal crest, several inherent morphological features like abnormal cordal principle of the repair is to sandwitch the superior and inferior and papillary architecture are the main causes of LVOT stenosis. bridging leaflets between the scoop out interventricular septum For complete AV canal defects, there are many studies comparing and pericardial patch. Closure of the cleaft and the rest of the defect the impact of their above mentioned techniques on operative are theDouble same Patchas in the Technique: classic single patch repair (Figure 7). mortality, late mortality, injury to the conducting system, left AV valve stenosis and insufficiency, residual ventricular level shunting, With this technique, atrial and left ventricular outflow tract obstruction and need for reoperation ventricular components of the defect are closed using separate for left AV valve insufficiency in the literature,. Comparison of the patches. For ventricular component, Dacron or PTFE material and studies of three different repair techniques are given in Table 1. Cite this article: 7720 Koray Ak. Atrioventricular Canal Defects: Morphologic Features and Surgical Techniques. Biomed J Sci&Tech Res 10(2)-2018. BJSTR. MS.ID.001930. DOI: 10.26717/ BJSTR.2018.10.001930. Biomedical Journal of Scientific & Technical Research Volume 10- Issue 2: 2018

Table 1: Comparison of three different surgical techniques in the literature (CSP: classic single patch, MSP: modified single patch, DP: double patch). In comparison, there have been more reports about the results of double patch repair in AV canal defects in the literature. In a meta- Total Early Late Late MV 3rd Degree analysis by Backer et al, a total of 889 patients who underwent AV Number of Mortality Mortality Reop Block (%) Pts (N) (%) (%) (%) canal repair using double patch technique was reported. Although CSP 4 the rates of early and late mortality were found to be similar among three techniques, the rate of late mitral valve regurgitation was said MSP 350 4.8 9.7 2.3 to be higher after double patch repair (Table 1) [11]. As is the case DP 200 2 0 2 0.5 for classic single patch technique, one of the main concerns about 889 3.5 2.1 7.2 2 double patch technique is division of AV valve leaflets during repair. It has been claimed that dividing the common leaflet and then In 2008, Crawford reported the results of 88 complete AV reattaching inevitably sacrifices valve tissue. This could be more canal defect patients who underwent repair via classic single important in infants in whom the scarified area constitutes a greater patch technique. There were no early and late mortality. Complete portion of the valve. In a study by Fortuna et al. [12], it was shown heart block was reported in 3 patients and 9 of the patients after that division of the common valve may lead to distortion of the procedure required mitral valve reoperation [4]. Prifti et al reported remaining valve tissue and increased tension on the cleft closure, their results with classic single patch technique in 190 AV canal leading to regurgitation and increased risk of cleft dehiscence. They patients weighing less than 5kg. The early and late mortality rate concluded that division of the bridging leaflets is a risk factor for were 8,4% and 7,4%, respectively. While the rate of complete heart AV valve regurgitation (moderate or greater) during the first year block was subtle (in only 3 patients), 23 patients needed late mitral after repair. In a report by Backer et al. [13], data related to 173 reoperation during follow up [5]. Similarly, in a report by Reddy et patients was published. The operative mortality was 6% and 4% of al. [6], 72 patients who underwent surgical repair via classic one the patients had pacemaker implantation for third degree AV block. patch technique were reported. Only one patient with early and 1 Moreover, 8% of the patients had reoperation for left AV valve in the with late mortality were given. Complete heart block was seen in 1 follow up. Similar results were given by other investigators [14]. In patient and none required late reoperation for mitral valve during conclusion, nowadays AV canal repair are done with low operative a median follow up of 24 months. The outcome of modified single- mortality and morbidity in many centers and outcome did not differ patch (Australian) technique in complete AV canal defects was Referencesby the surgical technique. initially described by Dr. Nunn [7] and the 30-day mortality rate 1. was reported as 1.6%. Jacobs ML, Jacobs JP, Jenkins KJ, Gauvreau K, Clarke DR, et al. (2008) The percentage of patients who needed reoperation on the Stratification of complexity: the Risk Adjustment for Congenital Heart mitral valve was reported to be 2.3% incidence of and none of the Surgery-1 method and the Aristotle Complexity Score--past, present, 2. patients had left ventricular outflow tract obstruction requiring and future. Cardiol Young 18 Suppl 2: 163-168. operation in the follow-up period. Jonas et al. [8] reported very Franklin RCG, Béland MJ, Colan SD, Walters HL, Aiello VD, et al. (2017) good results with almost zero morbidity and mortality after Nomenclature for congenital and paediatric cardiac disease: the International Paediatric and Congenital Cardiac Code (IPCCC) and the modified single patch technique. In a report by Backer et al, the Eleventh Iteration of the International Classification of Diseases (ICD- authors compared double patch technique with modified single 3. 11). Cardiol Young 27(10): 1872-1938. patch technique and stated that modified single patch technique is Manning PB (2007) Partial atrioventricular canal: pitfalls in technique. the best method of repair in complete AV canal defects [9]. Indeed, 4. Semin Thorac Cardiovasc Surg Pediatr Card Surg Annu p. 42-46. the cross-clamp and CPB times were significantly lower in modified Crawford FA (2007) Atrioventricular canal: single-patch technique. single patch group compared to the double patch group (26 and 5. Semin Thorac Cardiovasc Surg Pediatr Card Surg Annu 10: 11-20. 29 minutes shorter, respectively). Likewise, Wilcox et al reported Prifti E, Bonacchi M, Bernabei M, Adrian Crucean, Bruno Murzi, et al. the similar finding [10]. Backer et al. [9] insisted on the fact that (2004) Repair of complete atrioventricular septal defects in patients the major advantage of modified single patch technique is the 6. weighing less than 5 kg. Ann Thorac Surg 77(5): 1717-1726. avoidance of reoperation for mitral regurgitation in follow up and, Reddy VM, McElhinney DB, Brook MM, Parry AJ, Hanley FL (1998) therefore, they stopped doing double patch technique in 2006 and Atrioventricular valve function after single patch repair of complete atrioventricular septal defect in infancy: how early should repair be completely switched to modified single patch technique. On the 7. attempted? J Thorac Cardiovasc Surg 115(5): 1032-1040. other hand, it was speculated by some authors that the presence Nunn GR (2007) Atrioventricular canal: modified single patch technique. of a large ventricular component of the defect might jeopardize the 8. Semin Thorac Cardiovasc Surg Pediatr Card Surg Annu 10: 28-31. quality of repair modified single patch technique [10]. However, Jonas RA (2004) Complete atrioventricular canal. In RA Jonas, J DiNardo, this finding has net been supported by other authors [9]. Lastly, PC Laussen (Eds.), Comprehensive Surgical Management of Congenital the major critique of the modified single-patch technique was the 9. Heart Disease, Arnold Publishers, London, Uk, pp. 397-398. higher risk of post repair left ventricular outflow tract obstruction Backer CL, Stewart RD, Bailliard F, Kelle AM, Webb CL, et al. (2007) due to the pushing of the superior leaflet down toward the left Complete atrioventricular canal: a comparison of the modified single- ventricular outflow. Similarly, this finding was not supported by patch technique to the two-patch technique. Ann Thorac Surg 84(6): Jonas and Wilcox’ findings [8,10]. 2038-2046.

Cite this article: 7721 Koray Ak. Atrioventricular Canal Defects: Morphologic Features and Surgical Techniques. Biomed J Sci&Tech Res 10(2)-2018. BJSTR. MS.ID.001930. DOI: 10.26717/ BJSTR.2018.10.001930. Biomedical Journal of Scientific & Technical Research Volume 10- Issue 2: 2018

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Cite this article: 7722 Koray Ak. Atrioventricular Canal Defects: Morphologic Features and Surgical Techniques. Biomed J Sci&Tech Res 10(2)-2018. BJSTR. MS.ID.001930. DOI: 10.26717/ BJSTR.2018.10.001930.